1. Field of the Invention
The present invention relates to a grounding structure of a fuel tank (hereinafter referred to as PFT) made of resin, and in particularly, to a grounding structure of a fuel tank discharging static electricity that is charged on fastening members fixing a lid body that covers an opening of the fuel tank.
2. Description of the Related Art
Conventionally, in a fuel tank made of resin a fuel pump inserted inside the fuel tank is fixed in the fuel tank with being built in an attachment plate. Therefore, in the fuel tank an opening to attach the attachment plate is provided and the attachment plate built in the opening has a structure closing the fuel tank with liquid sealed therein. Static electricity occurring in a fuel tube equipped inside/outside the fuel tank connected to an intank system of fuel pump equipment is designed to be able to be simply discharged without an exclusive a grounding circuit being provided.
FIG. 6 is a section view showing an opening of a fuel tank related to a conventional example and shows an outline of a grounding structure of the fuel tank. As shown in FIG. 6, an upper plate 71 fixed in an opening 62a of a fuel tank 62 and a connector pipe 77 insert-molded in the upper plate 71 are formed of conductive resin, and moreover, a ground terminal 75 of a connector 74 for electrical wiring with contacting the upper plate 71 is insert-molded and fuel tubes 65a and 68a connected to both ends of the connector pipe 77 are formed of the conductive resin. Then due to friction in fuel flowing through the fuel tubes 65a and 68a, static electricity occurring in the connector pipe 77 is discharged outside the fuel tank 62 via the connector pipe 77, upper plate 71, and ground terminal 75 (for example, see pages 2 to 4 and FIG. 3 in Japanese Patent Laid-Open Publication 2001-271718).
However, in these years an improvement of sealing performance of a fuel tank is requested according to environmental regulations and the like. In the future, as the fuel tank it is foreseen that fastening members made of metal such as steel will further increase. Therefore, when the metal such as steel that is large in mass is used for fastening members to close the opening of the fuel tank made of resin, electrical charges due to static electricity are accumulated in a PFT (Plastic Fuel Tank) body and conductive fastening members floated by a seal and packing. That is, the electrical charges charged on the tank main body made of resin flow toward the fastening members made of metal, thereby the charging of the static electricity proceeds, and the members are being charged. Thus, an energy in a case of a conductive material being charged is higher compared with that of an insulator, and an influence in discharging also becomes enormous.
In other words, when the static electricity is accumulated on the fastening members made of metal such as a ring-shaped member and retainer, there exists a problem that: the accumulated static electricity is accumulated as it is since it has no place to escape to; and the electricity is instantly discharged.